they sell them at Ace Hardware.

Go to ace Hardware and buy. They have very sturdy ones. Better than a trowel.

I don't understand, why would you put donuts in the yard, are you hoping to attract some hungry police officers?

(it's a joke :) )

Ace Hardware in Wildwood sells a very good cutter for the doughnut rings. They are much stronger than what you will find and Lowe's or Home Depot. I use mine about every other month.

I respectfully disagree with your selection. The donut cutters available from Lowes or Home Depot are substandard in quality and durability. Neighbors have owned them and they struggled with cutting the grass roots (the cutting teeth are too short) and the strength of the welding. Failures occur when the welds break.

I purchased a heavy duty donut cutter from Florida Irrigation Service (FIS). They are located about 1 mile north of the intersection of CR42 and US441. Their donut cutter is a bit pricey, but worth the cost in reducing frustration.

OK, I learned something here. Of course, I do every day from this site!

Buy a donut cutter.

Quit using the sawzall to cut that damn grass.

Ace Hardware by Wedgewood lane sells the tool. Makes a perfectly round hole to fit the concrete donuts which Ace also sells.

Looks like you have received plenty of suggestions! I purchased the expensive heavy duty doughnut tool. It will be around long after I am gone. Also you may be interested in making your own sprinkler doughnuts, if you need to replace or add any.. the molds are 20 bucks and a bag of Quickset is 5.00...with the temperature warming up get a good pair of speedos and some flip flops...

Donut Tool
 

You can also use the tool from Lowe’s or Home Depot to trim around your underground downspout that have drains covers that are even with the lawn.

I think this is the good one:

Kenyon 85427 Sprinkler Head Trimmer, 7" Diameter with Step Plate, Welded 33" Overall Length, 5/8" Powder-Coated Structural Steel, T-Handle,

Me too but I guess some like a special tool for each job. Use a trowel, hands work well too. Much cheaper

ACE Hardware $25

Ace hardware carries the tool. Get the heavy duty version. This weed grass is dense.

Donut cutter
 

I bought a donut hole cutter from Lowe's and love it. It cost about $25.

Upgrade
 

Spend some more for the heavy duty one. I got mine at Ace Hardware. Glad I did.